Hierarchical control of droop-controlled DC and AC microgrids — a general approach towards standardization

DC and AC microgrids are key elements to integrate renewable and distributed energy resources as well as distributed energy storage systems. In the last years, efforts toward the standardization of these microgrids have been made. In this sense, this paper present the hierarchical control derived from ISA-95 and electrical dispatching standards to endow smartness and flexibility to microgrids. The hierarchical control proposed consist of three levels: i) the primary control is based on the droop method, including an output impedance virtual loop; ii) the secondary control allows restoring the deviations produced by the primary control; and iii) the tertiary control manage the power flow between the microgrid and the external electrical distribution system. Results from a hierarchical-controlled microgrid are provided to show the feasibility of the proposed approach.

I. Introduction

Microgrids (MG), also named minigrids, are becoming an important concept to integrate distributed generation (DG) and energy storage systems. The concept has been developed to cope with the penetration of renewable energy systems, which can be realistic if the final user is able to generate, storage, control, and manage part of the energy that will consume. This change of paradigm, allows the final user be not only a consumer but also a part of the grid.